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When to replace cartridges?

Hi all, sorry if this has already been answered but I couldn't seem to find it. I just bought a house in Dec 2008 with a 15k gunite pool, my filter is a sta-rite system 3. I found the manual online and have looked around the internet but could not find a good answer. I wanted to know from some experienced ppl when do you know if the cartridges need to be replaced? I have no idea how old they are, they could be 6 years old for all I know, they definitely don't look that new. I only get down to 15psi after cleaning them, should I expect a lower psi? What is the general guidance to replacing those other than obvious holes and tears?

Re: When to replace cartridges?

Cartridges can last quite a while if you take good care of them. Aside from an obvious hole or tear, they can eventually get clogged. A clogged cartridge shows up as the filter pressures starting quite high right after cleaning the cartridge, compared to the filter pressure observed when the cartridge was new. Since the filter pressure is specific to many details of your plumbing, this is difficult to determine without knowing the history of your system. A filter pressure of 15 psi isn't especially high, so it seems very likely that your cartridge is fine.

Re: When to replace cartridges?

I too, have a cartridge filter. Like Jason said, if you take care in cleaning them, you should get some years out of them.

They obviously need replacing when the filter membrane gets torn or when the little retaining strap that holds it together breaks or tears.

It is a good idea to have two sets of cartridges. That way, when you take the existing ones out to clean, you can quickly swap clean ones into the filter to get your pool back on-line quickly. Then your dirty ones can soak and be cleaned at your leisure and you pool can still be used. Once you have them clean, just let them dry and put them in storage until you need to swap out again.

One more thing...if you do buy a new set of cartridges, make note of what the filter pressure is as soon as you get the new ones installed. This is good information to have down the road as you will be able to tell when they need to be cleaned again often by the filter pressure alone.

Re: When to replace cartridges?

Thanks for the responses! I just have no idea about how old they are since I never spoke with the old owner when I bought the house. The retaining straps are quite worn looking and almost to the breaking point so while the filter seems to be working fine, I think they probably will need to be replaced now or after one more season. Thanks again for the replies.

Re: When to replace cartridges?

After you clean them you will notice about the same pressure drop as usual, only now the pressure will rise back up to your "need to clean" pressure within a week. Maybe even a couple of days.

As noted above, note the clean pressure on a new set. I would only change that to every time you clean as well. Just so you can keep track. The clean pressure may rise over time and that is normal wear.

Re: When to replace cartridges?

Ok, thank you, that's what I suspected. I just cleaned my filter, and it went down to 15PSI, which is about right, but it is almost already back to 25PSI and within only a few days. Just looking at them they seem really old, so I think it is probably about time to get some new ones. Thanks again for the info!

Re: When to replace cartridges?

Originally Posted by corsair2002

Ok, thank you, that's what I suspected. I just cleaned my filter, and it went down to 15PSI, which is about right, but it is almost already back to 25PSI and within only a few days. Just looking at them they seem really old, so I think it is probably about time to get some new ones. Thanks again for the info!

Yes, it may be time to get some. It is quite possible that they are 6 years old as you suggested and that is pushing the upper limits. When you clean them, they should be nice and white afterward.

Re: When to replace cartridges?

I have a DE filter and the same thing happend to me. I did a backwash and only did it two times. Then my pressure went down and 2-3 days later it was back up high. I did the backwash again and did it about 5 times, until when I did the backwash all that came out was clear water. Now my pressure dropped down to 10 and has risen not even to 15 and it has been about 3 months now. My pool does not get very dirty so that could be a reason it has stayed so low. I have vacummend a few times the past weekend and notice the pressure has risen a little but still under 15.

Re: When to replace cartridges?

I have a sta-rite system 3 as well and just wanted to make a couple of comments on the thread:

1) Other problems could result in quickly rising pressures as well. Last year when I had this problem, someone suggested that I might be on the verge of an algae outbreak (algae growing and being killed off before I really ever saw it). At their suggestion, I elevated my FC to 8-9ppm for a while and the filter stays clean a much more reasonable period of time now. When I was having this issue, the stuff I was rinsing off of the filter was kind of a grey slimy stuff. Just be aware of other potential issues before going out and dropping $5-700 on another set of filters (I don't know how big yours are, but that's about what mine seem to run. (my filter is only 3 years old so I haven't replaced it yet).

2) My restraining bands started coming unglued almost as soon as I had the pool installed. I found that hot melt glue seems to work really well for re-attaching them.

Re: When to replace cartridges?

Originally Posted by CurtisT

I have a sta-rite system 3 as well and just wanted to make a couple of comments on the thread:

1) Other problems could result in quickly rising pressures as well. Last year when I had this problem, someone suggested that I might be on the verge of an algae outbreak (algae growing and being killed off before I really ever saw it). At their suggestion, I elevated my FC to 8-9ppm for a while and the filter stays clean a much more reasonable period of time now. When I was having this issue, the stuff I was rinsing off of the filter was kind of a grey slimy stuff. Just be aware of other potential issues before going out and dropping $5-700 on another set of filters (I don't know how big yours are, but that's about what mine seem to run. (my filter is only 3 years old so I haven't replaced it yet).The scenario i described (earlier in this post) is with nothing drastic being done to the pool afterwards, i.e. trying to kill off an impending algae attack. Of course this will send more material to the filter and cause a premature pressure rise. My bad for not specifying. However, I would try to kill the algae off before i clean the filter. This way, you only have to clean the filter once.

2) My restraining bands started coming unglued almost as soon as I had the pool installed. I found that hot melt glue seems to work really well for re-attaching them. The "restraining Bands" are mostly for manufacturing, they help hold the pleats in place as the top and bottom pieces cool/bond to the element.

Re: When to replace cartridges?

One thing to try before giving up on a set of cartridges is to first do an overnight TSP soak. After that, and only after the TSP soak, do an acid soak (1:1). As was pointed out before, the PSI rise could be due to algae so make sure that is killed before cleaning the filters.

Re: When to replace cartridges?

Originally Posted by mas985

One thing to try before giving up on a set of cartridges is to first do an overnight TSP soak. After that, and only after the TSP soak, do an acid soak (1:1). As was pointed out before, the PSI rise could be due to algae so make sure that is killed before cleaning the filters.

Normally, i would agree. But after >6 years? I'm not sure i would spend the time on them (these days...).

Re: When to replace cartridges?

Originally Posted by mas985

One thing to try before giving up on a set of cartridges is to first do an overnight TSP soak. After that, and only after the TSP soak, do an acid soak (1:1). As was pointed out before, the PSI rise could be due to algae so make sure that is killed before cleaning the filters.

Re: When to replace cartridges?

Hijacking just a little....
I don't have any experience with a cartridge filter but my assumption was they went bad when they were damaged and developed holes....something that would allow dirt through (and drop pressure).

However, If I am reading this thread correctly, it seems cartridges can clog up irreversibly at some point and that is a more common end to the filters life. Am I misinterpreting?

Re: When to replace cartridges?

Originally Posted by frustratedpoolmom

Originally Posted by mas985

One thing to try before giving up on a set of cartridges is to first do an overnight TSP soak. After that, and only after the TSP soak, do an acid soak (1:1). As was pointed out before, the PSI rise could be due to algae so make sure that is killed before cleaning the filters.

Re: When to replace cartridges?

Cleaning a cartridge, even the overnight detergent soak followed by an acid soak, never removes everything. So, yes physically intact but "well used" cartridges do eventually need to be replaced. However, with proper care this won't happen for a good long time.

Re: When to replace cartridges?

Originally Posted by Pool Clown

Originally Posted by CurtisT

2) My restraining bands started coming unglued almost as soon as I had the pool installed. I found that hot melt glue seems to work really well for re-attaching them. The "restraining Bands" are mostly for manufacturing, they help hold the pleats in place as the top and bottom pieces cool/bond to the element.

This is news to me and I'm awfully glad to hear it. I think on another thread a few months ago someone implied that the bands breaking spelled the end of usefulness for the cartridge. Though several of the bands have broken off on the 4 behemoths residing inside my SwimClear C4025 filter (due to clumsy cleaning technique by yours truly) performance is A-OK, the pleats are intact and the material, bright white.

Re: When to replace cartridges?

Some of the bands on my cartridge filter started to break after around 3-4 years. Quite a few were broken after the 7th year (last year) when I decided to replace the cartridges. The fabric material wasn't torn so I probably could have gone longer, but I just figured on getting some new ones so that's what I did. I only need to clean them once a year since I've got an oversized filter with 4 cartridges (340 square foot total for a 16,000 gallon pool) and my pool keeps fairly clean due to an electric safety cover (though I do get a fair share of cedar needles, some of which make it all the way to the filter).

This year, we cut down the cedar tree as we just got fed up cleaning off the cover so frequently so we'll see how it goes with getting such needles in the skimmer basket, pump basket and filter cartridges. It was a tough choice as that tree gave some definition to the yard, but it just wouldn't listen to us about dropping it's needles . Fortunately, we've got lots of other foliage and the additional sunlight during the late day on the solar panels may help reduce our heating costs during spring and fall.

Re: When to replace cartridges?

I ended up getting new cartridges. The old ones definitely look pretty beat up compared to the new ones, not just dirty, but worn, and the filter media doesn't look good, even when "cleaned". One of the things I noticed about the old ones was that they were causing the air filter to become clogged with these little white slivers of what I can only assume is the filter media, they look like white pine needles. I think it was definitely time to get new ones. I am thinking that those are the original cartridges, so they are probably over 5 years old. Anyway, the water is looking nice, and the pressure is staying stable and not increasing quickly like with the old ones...I am happy now!